Signal processing is a very important part of modern technology. It is used in a wide variety of fields, such as in high-speed printing, image processing and telecommunications. Optical signals especially have become very important in recent years, since light travels at maximum speed and may not be vulnerable to interference problems that trouble electrical signals. As the definition of a composite signal increases by adding more pixels per inch, etc., it becomes necessary for signal processing equipment to handle larger and larger numbers of discrete signals in a smaller and smaller area. Equipment that switches the optical signals in these discrete channels must thus also be reduced further and further in size, a trend which has lead to the development of arrays of micro-switches.
These micro-switches can be made in a number of ways. A first type of switch uses electro-optically active material which can change its index of refraction or polarity when an electric field is applied. This type of switch can be effective, but may require the use of expensive materials, and generally require relatively high activation voltages.
Micro-machined devices of silicon (MEMS) is another approach to the fabrication of micro-switches. As the name implies, a wafer of silicon is machined by any number of processes including micro-sawing, etching, etc. to create a switching element which is free to move in some direction, either linearly or rotationally so that a signal can be directed from a first signal path into a second signal path as required. An actuator device is generally needed to move the switching element, and a problem has existed in getting each of these switching elements in an array which may include hundreds or thousands to go to precisely the same position when activated, and to return to the same position when deactivated. Since the spatial location of each incoming and outgoing beam must be precisely defined, if the switching element is not also precise in its positioning in both the activated and deactivated states, signal information may be distorted or lost.
Prior art switches include cantilever shafts which allow a switch element to be raised and lowered in and out of a beam path. These are less versatile and reliable than would be desired. It would be preferred to use switches in which the switching elements are free-standing, that is, completely unattached to the surrounding matrix material, however, these are difficult to produce and precise orientation of each of a great number of microscopic elements can be difficult to achieve.
Accordingly, there is a need for a micro-switch which can be made individually very small, and for which large multiples can be manufactured in large arrays. There is also a need for micro-switches which require only small activation voltages, are reliable, cost effective, and assume very precise positions both when activated and deactivated.
In addition, signal processing is a very important part of modern technology. It is used in a wide variety of fields, such as communications, data transmission, and testing. Switches of this nature can neatly fill the gap that exists between conventional silicon transistors and electromagnetic “macro-mechanical” reed relays and compete with electrostatic actuated micro-relays. Silicon transistors have the drawback of having finite “off resistance” and fairly large “open resistance” as compared to electromagnetic reed relays. Reed relays, on the other hand, typically dissipate a good deal of current (generating heat). Electrostatic relays do not carry the large currents of reed relay switches and does not have a strong applied force at the point of contact. Since reliability is of the utmost import in the relay business, and reliability is directly related to contact force, there are disadvantages to these kinds of switches.
Micro-machined devices made of silicon (MEMS) offer another approach to the fabrication of micro-switches. As the name implies, a wafer of silicon is machined by any number of processes including micro-sawing, etching, etc. to create a switching element which is free to move in some direction, either linearly or rotationally so that a contact can be made. An actuator device is generally needed to move the switching element, and a problem has existed in getting each of these switching elements in an array which may include hundreds or thousand to go to precisely the same position when activated, and to return to the same position when deactivated.
Thus, there is a need for a micro-switch which can be made individually very small, and for which large multiples can be manufactured in large arrays. There is also need for micro-switches that emphasize full switch functionality and manufacturability and provide strong contact force.